linux-kernel - [PATCH v5] media: pci: intel: ivsc: improve device reference counting in mei

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Message-Id: <20250929013007.1920-1-make24@iscas.ac.cn>
Date: Mon, 29 Sep 2025 09:30:07 +0800
From: Ma Ke <make24@...as.ac.cn>
To: sakari.ailus@...ux.intel.com,
	bingbu.cao@...el.com,
	lixu.zhang@...el.com,
	stanislaw.gruszka@...ux.intel.com,
	mchehab@...nel.org,
	wentong.wu@...el.com
Cc: linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	Ma Ke <make24@...as.ac.cn>
Subject: [PATCH v5] media: pci: intel: ivsc: improve device reference counting in mei_ace driver

The device reference counting in mei_ace_setup_dev_link() was
incomplete, as the reference acquired by device_find_child_by_name()
was not released immediately on the success path. Add put_device() to
properly balance the reference count. Additionally, the redundant
put_device() in mei_ace_remove() is removed.

Found by code review.

Signed-off-by: Ma Ke <make24@...as.ac.cn>
---
Changes in v5:
- jumped to err instead of err_put to avoid calling put_device() again in err_put as reviewer's instructions;
Changes in v4:
- updated the subject as suggestions;
Changes in v3:
- deleted the tag of Fixes and CC, and moved put_device() to immediately after device_link_add() as suggestions;
Changes in v2:
- modified the put_device() operations and the patch title as suggestions.
---
 drivers/media/pci/intel/ivsc/mei_ace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/pci/intel/ivsc/mei_ace.c b/drivers/media/pci/intel/ivsc/mei_ace.c
index 98310b8511b1..b306a320b70f 100644
--- a/drivers/media/pci/intel/ivsc/mei_ace.c
+++ b/drivers/media/pci/intel/ivsc/mei_ace.c
@@ -414,10 +414,11 @@ static int mei_ace_setup_dev_link(struct mei_ace *ace)
 	/* setup link between mei_ace and mei_csi */
 	ace->csi_link = device_link_add(csi_dev, dev, DL_FLAG_PM_RUNTIME |
 					DL_FLAG_RPM_ACTIVE | DL_FLAG_STATELESS);
+	put_device(csi_dev);
 	if (!ace->csi_link) {
 		ret = -EINVAL;
 		dev_err(dev, "failed to link to %s\n", dev_name(csi_dev));
-		goto err_put;
+		goto err;
 	}
 
 	ace->csi_dev = csi_dev;
@@ -522,7 +523,6 @@ static void mei_ace_remove(struct mei_cl_device *cldev)
 	cancel_work_sync(&ace->work);
 
 	device_link_del(ace->csi_link);
-	put_device(ace->csi_dev);
 
 	pm_runtime_disable(&cldev->dev);
 	pm_runtime_set_suspended(&cldev->dev);
-- 
2.17.1